A pulse combustor is a device in which a mixture of air and fuel is initially ignited by, for example, a ignition rod. The ignited gases expand rapidly with an associated rapid increase in pressure and temperature. A resultant pressure wave travels down the device expelling the burnt gases out of an exhaust region. Heat exchange occurs at the walls of the device cooling the gases and enhancing the pressure drop occurring after passage of the pressure wave. This pressure drop due to expansion of the gases combined with the cooling caused by heat exchange at the walls causes new gases to be drawn into the combustion chamber. At the same time the flow in the exhaust region reverses and compresses the new air and gas mixture and with the temperature in the combustion chamber still being high ignition occurs once again.
U.S. Pat. No. 4,968,244 issued to the Inventor herein, Mehrzad Movassaghi, describes a pulse combustor with a radial exhaust chamber and a carburetor coupled to the combustion chamber for injecting a pre-determined distribution of fuel mixture into the combustion chamber. The design of the casing of the exhaust chamber comprises an inside disc and an outside disc juxtaposed thereto with an inside disc and outside disc located on each side of the combustion chamber. The exhaust chamber has a spiral groove in the inside disc which is covered by the outside plate forming a coolant passageway. The usage of a disc and plate bonded together with a spiral groove in the disc makes construction difficult and expensive. Moreover, the rapid heating and cooling stresses the bonding between the disc and plate making the device susceptible to coolant leaks. Finally, the somewhat complex design of the carburetor adds to the expense of the device.
In known heat generation systems in either a boiler or furnace, control is achieved by turning the heat generating system on and off. When the temperature exceeds a preset threshold, the system is turned off and allowed to cool. Similarly, once cooling has lowered the temperature below a threshold, the system is restarted. Obviously, heating above the threshold on heating up and cooling below the threshold on cooling down are inherent in such a control system. The constant cycling between the temperatures at shut-off and turn-on contribute to high thermal stresses which reduce the life expectancy of the material.
In addition, known heat generation systems in either a boiler or furnace optimize the combustion reaction by controlling the gas flow in relation to the air flow. The degree of optimization of the reaction in these systems depends on the accuracy of the means for measuring the flow of gas and air and the means for controlling the flow of gas. Also, in these systems, the reactant of the combustion reaction, oxygen, is not measured directly. Thus, variations in the amount of oxygen in the air due to ambient air quality or altitude which would affect the reaction rate are ignored.
European. Pat. No. 0 317 178 discloses a simple boiler having a combustion chamber adjacent a fluid chamber from which it receives heat. A temperature control system with two temperature sensors whose temperature measurements are transmitted to an electrical control box is disclosed. A motor speed controller linked to the electrical control box responds to an increasing temperature differential by causing the motor of a fan to speed up thereby increasing the amount of air in the air chamber. An air pressure sensor tube which opens into the chamber senses the air pressure and actuates a diaphragm which changes the gas flow by means of a gas regulator valve accordingly. The air chamber also contains a flame ring at one end which opens onto the combustion chamber. There is no measurement of the gas flow pressure. Thus, the means for controlling the gas to air fuel ratio is relatively simple. Also, the gas line introduces the gas into this flame ring and the gas and air are mixed at the flame ring instead of a mixing chamber.
In Japanese. Pat. No. 58 085 016, a boiler has an air sensor and a gas sensor to sense the amount of air and gas supplied respectively. The amount of gas supplied is changed in response to the amount of air supplied. The speed of the fan which determines the amount of air supplied is controlled by signals from a temperature sensor coupled to the heat exchanger. The signals from the air sensor and the gas sensor are sent to a gas flow rate control unit which controls the closing and opening of the a control valve in the gas line. There is also premixing of gas and air before combustion, however, the premixing occurs in the air chamber where the air sensor is located. As the gas line emits gas into the air chamber, the measurement of air pressure may be skewed.
The efficiency of the combustion in systems which establish the air-gas ratio from a measurement of the air pressure differential across an aperture and an adjustment of the gas flow accordingly, or some other equivalent method, are affected by factors such as efficiency of mixing of the gas and air, barometric pressure, extremes of temperature, and the presence of gas in the air flow measurement. None of the foregoing systems address solutions for these inaccuracies.
Accordingly, it is an object of the invention to provide a less costly, more efficient and reliable radial pulse combustor than is presently known. It is a further object of the invention to provide a boiler which utilizes the aforesaid pulse combustor and in which control of the output temperature is applied continuously. It is further an object of the invention to provide a pulse combustor with maximum rates of combustion.